1. Technical Field
The present invention generally relates to wireless transmission systems and in particular to calibration of a radio frequency head in wireless transmission systems.
2. Description of the Related Art
Wireless systems regularly broadcast independent radio frequency (RF) signals using smart antenna operation. However, these wireless systems may occasionally combine independent signals before broadcasting the combined signals over the orthogonal frequency division multiple access (OFDMA) air interface. In particular, the wireless system may broadcast independent signals for a particular time interval and broadcast the combined output signals during another time interval. Separate calibration mechanisms are conventionally required for the transmission of independent signals and the transmission of the combined signals. These different calibration mechanisms are generally accommodated by separate sets of dedicated hardware. In addition, the RF components of the transmitter and receiver branches of the different antenna elements usually have different properties.
Thus, in order to support the various deployment options, a number of distinct product variants are generally used to serve multiple markets. As a result, RF Head complexity is increased. Ultimately, costs continue to escalate as wireless base stations integrate support for an increasing set of services.